For protecting children, starting from 1993 to 1994, the U.S. Consumer Product Safety Commission declared that the traditional disposable lighter should not be sold. Moreover, the U.S. Consumer Product Safety Commission imposed an important regulation that "Child below 4 years old cannot light the lighter".
Accordingly, various kinds of disposable lighters having switching mechanisms for rendering the lighters child resistant have been developed. Such switching mechanisms provide a switch member requiring the adult user to turn it on before permitting an operating lever to be depressed to lift a gas pipe to open a gas release valve while a spark is generated by simultaneous rotation of a striker wheel in engagement with a flint. However, such conventional gas lighters with switching mechanisms also bear the drawbacks as follows:
1. Numerous additional elements of the switching mechanism are required to incorporate with the traditional disposable lighter for ensuring the safety thereof. Such a costly switching mechanism not only increases the cost of the disposable lighter, but also increases the manufacturing procedures of the disposable lighter.
2. During the igniting operation of the gas lighter, initially, an additional step of turning the switch member of the switching mechanism to release the locking of the operating lever is needed for enabling the depressing of the operating lever to lift the gas pipe to open the gas release valve, which complicates the manipulation of ignition.
As mentioned above, most disposable lighters incorporated a switching mechanism to lock the gas lever or the spark wheel to prevent children from starting a fire. However, children are excellent in learning. Some smart or brilliant children may learn from an adult to release such switching mechanism and ignite the fire. Accordingly, it is not a wise way of trying to lock the spark wheel or the gas lever. In fact, the normal pressure of a thumb of a 4 years old child is about 1 kg. The maximum pressure of the thumb is not over 1.5 kg. The normal procedure for lighting the disposable lighter is to press the side and spark wheel so as to spark the flint and light a fire. At the same time, the lever must be pressed down to release the gas (the normal pressure to release gas is 0.5 to 1 kg) Therefore, a better way to prevent the children from igniting a lighter is to design a safety lighter that the child below 4 years old does not has the enough strength to ignite it.
A typical example, disclosed in a U.S. Pat. No. 5,096,414 owned by Zellweger, comprises a striker wheel acting on a spark stone. The striker wheel is disposed between two plates of greater diameter than and freely rotatable with respect to the wheel. Actuation of this lighter is obtained by friction thanks to the deformation of the pulp of the thumb of the user. Therefore, the striker wheel may not be driven by a child, as the pulp of the finger of a child is not sufficiently thick.
U.S. Pat. No. 5,547,370, owned by Hwang, is a further improvement of Zellweger's patent. Similar to Zellweger's patent Hwang's patent also includes a wheel axle mounted between two upright supports at the top of a butane wheel, two driving wheels mounted around the wheel axle between the upright supports, and a striker wheel fixedly mounted around the wheel axle and disposed in contact with a spring-supported flint below the striker wheel. The striker wheel is turned by the driving wheels through the wheel axle to strike the spring-supported flint in producing sparks. The improvement is that the wheel axle is made of polygonal cross section, having two round rods at two opposite ends loosely inserted into a respective axle hole on each upright support so as to ensure a better connection between the striker wheel and the wheel axle.
However, Zellweger's and Hwang's patents still bear the following drawbacks:
1. The assembly cost is higher because special care and measurement must be applied to ensure the striker wheel is located in a center position of the wheel axle. Especially in Hwang's patent, the central polygonal hole of the striker wheel must be exactly equal to the size of the polygonal wheel axle. If it is too small, it is impossible to insert the wheel axle therethrough. If it is too big, the striker wheel may not be firmly held in center position. How to punch in the polygonal wheel axle through the polygonal hole of the striker wheel and how to ensure the striker wheel located in the center position of the wheel axle become the headaches of Hwang's patent.
2. Accordingly, a slight clearance would exist between the striker wheel and the wheel axle so as to facilitate insertion of the polygonal wheel axle through the central polygonal hole of the striker wheel. Normally, the rotation of the wheel axle can drive the striker wheel to rotate with no problem. However, the striker wheel may gradually move aside after using for a period of time. If such condition happens, the center of the striker wheel will not remain aligning with the flint properly, that may unavoidably affect the ignition of the lighter. Malfunction may also occur. The tip of the flint may get stuck between the driving wheel and the striker wheel.
3. In view of Hwang's patent, the driving wheels are not equipped to directly drive the striker wheel to rotate. In fact, the driving wheels must first to drive the wheel axle to rotate and then the striker wheel is driven to rotate by the rotating wheel axle. Since the size of the wheel axle is much smaller than the striker wheel, therefore even some adult will find it difficult to ignite the lighter.